//构造哈夫曼树和生成哈夫曼编码
# include <stdio.h>
# include <string.h>
# define N 50
# define M 2 * N - 1
typedef struct
{
    char data[5];
    int weight;
    int parent;
    int lchild;
    int rchild;
} HTNode;
typedef struct
{
    char cd[N];
    int start;
} HCode;
void CreateHT(HTNode ht[],int n)
{
    int i,k,lnode,rnode;
    int min1,min2;
    for (i=0;i<2*n-1;i++)
        ht[i].parent=ht[i].lchild=ht[i].rchild=-1;
    for (i=n;i<2*n-1;i++)
    {
        min1=min2=32767;
        lnode=rnode=-1;
        for (k=0;k<=i-1;k++)
        if (ht[k].parent==-1)
        {
            if (ht[k].weight<min1)
            {
                min2=min1;rnode=lnode;
                min1=ht[k].weight;lnode=k;
            }
            else if (ht[k].weight<min2)
            {
                min2=ht[k].weight;rnode=k;
            }
        }
    ht[lnode].parent=i;ht[rnode].parent=i;
    ht[i].weight=ht[lnode].weight+ht[rnode].weight;
    ht[i].lchild=lnode;ht[i].rchild=rnode;
    }
}
void CreateHCode(HTNode ht[],HCode hcd[],int n)
{
    int i,f,c;
    HCode hc;
    for (i=0;i<n;i++)
    {
        hc.start=n;c=i;
        f=ht[i].parent;
        while (f!=-1)
        {
            if (ht[f].lchild==c)
                hc.cd[hc.start--]='0';
            else
                hc.cd[hc.start--]='1';
            c=f;f=ht[f].parent;
        }
        hc.start++;
        hcd[i]=hc;
    }
}
void DispHCode(HTNode ht[],HCode hcd[],int n)
{
    int i,k;int sum=0,m=0,j;
    printf("输出哈夫曼编码:\n");
    for (i=0;i<n;i++)
    {
        j=0;
        printf("  %s:\t",ht[i].data);
        for (k=hcd[i].start;k<=n;k++)
        {
            printf("%c",hcd[i].cd[k]);
            j++;
        }
        m+-ht[i].weight;
        sum+=ht[i].weight;
    }
    printf("\n平均长度=%g\n",1.0*sum/m);
}
int main()
{
    int n=15,i;
    char *str[]={"The","of","a","to","and","in","that","he","is","at","on","for","His","are","be"};
    int fnum[]={1192,677,541,518,462,450,242,195,190,181,174,157,138,124,123};
    HTNode ht[M];
    HCode hcd[N];
    for (i=0;i<n;i++)
    {
        strcpy(ht[i].data,str[i]);
        ht[i].weight=fnum[i];
    }
    CreateHT(ht,n);
    CreateHCode(ht,hcd,n);
    DispHCode(ht,hcd,n);
    return 1;
}